Puerto Rico, the shining star of the Caribbean, trumpeted an old ad campaign promoting the island’s dazzling beach-resort casinos and glitzy late-night bars throbbing with salsa and rumba bands. Stars, of course, have more than one face. Old San Juan—the historic district of Puerto Rico’s walled capital city—maintains a quieter bearing, one conveyed in sandstone fortresses and centuries-old churches and, perhaps most indelibly, one former nunnery.

San Juan was founded by the Spaniards in 1521 and served as both a stopover for ships sailing between Spain and America and a stronghold against Spain’s French, Dutch and English enemies. The hostilities greatly reduced the marriage prospects of the women on the island—and in 1646 one war widow, Dona Ana de Lansos y Menendez de Valdez, petitioned the government to establish a Carmelite convent there. Across from San Juan Cathedral (one of the oldest in the Western Hemisphere), the soldiers garrisoned in the city erected a graceful three-story structure of sun-baked clay. It featured a high-domed chapel, a spacious courtyard cloister and tiers of tiny nuns’ cells where, for the next 250 years, the sisters of the Mon-astery of Our Lady Carmen of San Jose would pursue their lives of contemplation.

The U.S. military took over Old San Juan during the Second World War, by which time the convent had assumed the form of a flophouse. After the war, the city was largely abandoned, its venerable buildings further declining (the flophouse became a parking lot for garbage trucks). But jet travel and government-sponsored renewal efforts sparked a comeback. Old San Juan’s friends in need included Robert Frederick Woolworth, who dipped into his department store inheritance to purchase the convent and turn it into El Convento, a five-story luxury hotel. Cells gave way to guest rooms; the nuns’ cloister served as a gracious public patio; the chapel was reborn as a popular venue for dining and flamenco shows.

“There was a tremendous explosion of tourism here in the ’60s,” recalls Hugh Andrews, who first visited Old San Juan as a ship hand and in 1994 acquired El Convento with several partners (he currently serves as the hotel’s president). “But the people who came here were artists and musicians and expats. And the people who came to El Convento were people who didn’t want to be stuck in the middle of a resort with a golf course.” People, that is, like Truman Capote and Pablo Casals (who practiced his cello in the courtyard), Ernest Hemingway and Gloria Vanderbilt.

By the time Andrews took over the hotel, the Spanish colonial beauty had taken another slide. “It was a shadow of itself,” he says, citing the wallboard that concealed courtyard arches and the red carpet that masked marble and clay tile floors. “We wanted to open it as a smaller boutique hotel, for people looking for something unique that reflects the culture of where they are. But it needed a lot of TLC.” On that account, El Convento was shuttered for a two-year, $15 million makeover.

Architect Rene Jean and Jorge Rosselló, one of Andrews’s partners and the project’s interior designer, reduced the number of guest rooms from 100 to 58. All are situated on the upper floors; a discreet reception desk is on the third floor. The two lower floors were given over to restaurants and shops. “We opened a new entrance from the street so you could access the central courtyard from there,” explains Rosselló. “The courtyard had been covered with an acrylic top that we removed to open it to the sky. We added an elevator, a gazebo next to the desk and a small terrace and swimming pool on the fourth floor.”

The additions were conceived in a simple, contemporary vein so that they wouldn’t compete with the original architecture. “The building, per se, didn’t suffer major changes,” reports Rosselló. “We just patched it up.” The tile floors were recovered; worn plaster walls were rejuvenated with earth-toned faux finishes; ancient wood beams and wrought iron torches were redeemed. Ros-selló salvaged whatever 17th-century furniture and paintings he could and rounded out the furnishings with re-production pieces.

Ringing the courtyard’s 300-year-old nispero tree, the guest rooms conjure the Old World spirit with mahogany beams overhead and Andalusian tiles underfoot. The Vanderbilt Suite honors its namesake with vaulted ceilings and checkered marble floors. More contemporary touches, like data ports on the phones and step machines in the spa, indulge patrons who “don’t want a cookie-cutter hotel but don’t want to sacrifice creature comforts,” according to Andrews. “We’re really more like a private club.”

A handful of small bars and cafés overlooking the courtyard turn out piña coladas, tapas, fresh seafood and other local staples. Old San Juan is gaining a reputation for its Nuevo Latino cuisine, and dozens of vibrant restaurants within walking distance of the hotel wed Caribbean fare—shrimp, plantains, fiery spices—with European flair. Many establishments feature music and dancing—and for the tireless, there are the after-hours spots, serving up tropical sounds and tropical potions courtesy of the nearby Bacardi plant.

By day, the Old San Juan beat tends to be no wilder than a walking tour through the district’s cobblestone streets. The ocher citadel of Castillo San Felipe del Morro facing down the blue Atlantic, the domed churches and pastel homes, the profusion of galleries and museums—the town itself is a museum, a relic of conquistador culture. “It’s almost like another world,” says Hugh Andrews. “You can disappear in the crowd here. There are people who wouldn’t appreciate my giving out their names but who come down, put on their dark glasses, and nobody knows they’re here.”